Water quality detection method for detecting heavy metal elements in water

Abstract

The invention relates to a water quality detection method for detecting heavy metal elements in water, which comprises the following steps: S1, pretreating a water sample, and filtering to remove suspended particles and impurities; s2, acid digestion of the sample: digesting the sample by using a mixed solution of nitric acid and hydrochloric acid to release heavy metal elements; s3, electrochemical sensor detection: anodic stripping voltammetry (ASV) or differential pulse voltammetry (DPV) is adopted for detection, and the sensor uses a gold-plated electrode or a glassy carbon electrode modified with carbon nanotubes and graphene; s4, concentration calculation: calculating the heavy metal concentration according to a current peak value and a volume correction formula; and S5, verifying a result, and rechecking a detection result by adopting an ICP-MS or AAS method. The method is high in sensitivity, can accurately detect trace heavy metals in drinking water, industrial wastewater, surface water and underground water, is suitable for simultaneous detection of multiple elements, has the advantages of simplicity and convenience in operation, portability of equipment, high detection speed and the like, and is particularly suitable for on-site water quality monitoring.

Description

Technical Field

[0001] The invention relates to the technical field of water quality detection, and in particular to a water quality detection method for detecting heavy metal elements in water. Background Art

[0002] Heavy metal pollution in water bodies is a major challenge in today's global environmental issues. With the rapid development of industrialization and urbanization, a large amount of industrial wastewater and domestic sewage are discharged into water bodies without treatment or treatment that does not meet standards, resulting in a gradual increase in the content of heavy metals in water bodies. The main sources of heavy metal pollution come from wastewater discharged from industries such as metallurgy, electroplating, pharmaceuticals, chemicals, and mining. The accumulation of heavy metal elements such as lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), and arsenic (As) in water bodies is long-term and non-degradable, and eventually enters the food chain through the water cycle, posing a serious threat to the ecological environment and human health.

[0003] Heavy metal ions in water not only have a fatal impact on aquatic plants and animals, but also directly affect human health through drinking water. Studies have shown that heavy metal elements such as lead will damage the nervous system, blood circulation system and kidneys after entering the human body, and may even cause cancer. Mercury and its compounds are highly neurotoxic, and the accumulation of cadmium can lead to renal failure. Long-term drinking of water containing excessive amounts of heavy metals such as cadmium and chromium can also cause bone and lung diseases. Therefore, how to effectively and quickly detect the content of heavy metal ions in water, especially low concentrations of trace heavy metal elements, has become an important topic in current environmental monitoring.

[0004] At present, the methods for detecting heavy metal ions in water mainly include the following categories: atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), and electrochemical analysis.

[0005] Atomic absorption spectrometry is currently the most widely used method for heavy metal detection. Its basic principle is to atomize the heavy metal elements in the sample through a high-temperature flame or graphite furnace, and use the element's absorption of light of a specific wavelength to quantitatively analyze the concentration of the metal. This method has high sensitivity and can detect heavy metal elements at lower concentrations. However, AAS requires a complex sample processing process, the equipment is bulky, and the detection speed is relatively slow, making it unsuitable for rapid on-site detection. In addition, AAS has a weak ability to detect multiple elements simultaneously, and usually requires multiple operations to complete the detection of multiple heavy metal elements.

[0006] ICP-MS is a highly sensitive heavy metal detection technology based on the principle of mass spectrometry. This method uses high-temperature plasma to ionize heavy metal elements in the sample, and then analyzes the mass of these ions through a mass spectrometer. ICP-MS has extremely high sensitivity and accuracy, can detect trace levels of heavy metal elements, and can detect multiple heavy metal ions at the same time. However, ICP-MS equipment is expensive, complex to operate, and has high requirements for laboratory environment. It is not suitable for large-scale popularization and application, especially in terms of rapid on-site detection.

[0007] XRF is a non-destructive detection method that uses X-rays to excite the fluorescence of elements in the sample and determines the type and content of heavy metals in the sample by analyzing the fluorescence spectrum. The advantage of XRF is that it can detect quickly and does not require complex sample pretreatment, and is particularly suitable for detecting heavy metals in solids or sediments. However, XRF has low sensitivity in detecting trace heavy metals in water, and has poor detection effect on some heavy metals with low atomic numbers.

[0008] Electrochemical methods are a type of heavy metal detection technology based on the principle of electrochemical reaction, mainly including anodic stripping voltammetry (ASV), differential pulse voltammetry (DPV), etc. Electrochemical detection methods have the advantages of simple operation, low equipment cost, and high sensitivity. They are especially suitable for rapid on-site detection and quantitative analysis of trace heavy metals in water. Anodic stripping voltammetry enriches heavy metal ions on the surface of the working electrode by applying a certain potential, and then dissolves the enriched heavy metals through changes in potential to generate current signals for quantitative analysis of heavy metal concentrations. Differential pulse voltammetry reduces background noise and enhances signal resolution through changes in pulse potential, making it more sensitive to the detection of trace heavy metals. Compared with other spectral detection methods, the outstanding advantages of electrochemical methods are that they can achieve rapid on-site detection, portable equipment, and are suitable for large-scale environmental monitoring needs.

[0009] Although existing detection technologies have made significant progress, there are still some challenges and limitations in practical applications:

[0010] Although traditional detection methods such as AAS and ICP-MS have high sensitivity, they are usually only suitable for single element analysis, especially in water bodies polluted by multiple heavy metals, the detection efficiency is low. Although the existing electrochemical detection method can realize the simultaneous detection of multiple elements, it still has certain limitations in the separation and selectivity of different heavy metals.

[0011] Most spectroscopic methods such as ICP-MS and XRF are bulky and expensive, making them unsuitable for on-site or mobile monitoring. Although electrochemical methods have relatively low equipment costs, how to further improve the portability and automation of the equipment without affecting sensitivity and selectivity remains an important research direction.

[0012] Other substances in the water, such as organic compounds, suspended particles, dissolved oxygen, etc., may interfere with heavy metal detection. These interferences will cause fluctuations in the detection signal and affect the accurate measurement of heavy metal concentrations. Therefore, how to maintain the stability of the detection results under complex water quality conditions is a major technical challenge.

[0013] In surface water and drinking water, heavy metals are usually present at trace levels, which places high demands on the sensitivity of detection technology. Existing detection methods may be limited by equipment sensitivity and detection errors when detecting trace amounts, resulting in biased results.

[0014] In view of the shortcomings of the existing technology, the present invention proposes a method for detecting heavy metal elements in water based on electrochemical detection, which combines the steps of water sample pretreatment, acid digestion, electrochemical sensor detection and concentration calculation to achieve efficient and rapid detection of multiple heavy metal elements in water. Compared with traditional detection technology, the present invention has the following advantages:

[0015] The present invention adopts an electrochemical detection method, the equipment is portable, low-cost, and can quickly detect a variety of heavy metal elements under complex water quality conditions. It is particularly suitable for on-site detection and large-scale environmental monitoring.

[0016] The present invention adopts a combination of anodic stripping voltammetry (ASV) and differential pulse voltammetry (DPV), which can effectively reduce background noise and improve signal resolution, so that trace heavy metal elements can still be accurately detected under low concentration conditions.

[0017] By optimizing the design of electrochemical sensors and electrode modification technology, the present invention can simultaneously detect multiple heavy metal elements and achieve better selective separation of different elements, thus overcoming the problem of low efficiency of multi-element detection in existing methods.

[0018] The detection method of the present invention is applicable to a variety of water samples, including different types of water bodies such as drinking water, surface water, industrial wastewater, etc., and can maintain the stability and accuracy of detection under different water quality conditions.

[0019] In summary, the present invention provides a water quality detection method for detecting heavy metal elements in water, which overcomes the limitations of the prior art and has broad application prospects. Summary of the invention

[0020] The purpose of the present invention is to provide a water quality detection method for detecting heavy metal elements in water in view of the shortcomings of the prior art, comprising the following steps:

[0021] S1: Water sample pretreatment: Filter the water sample to be tested through a filter membrane with a pore size of 0.45 microns to remove suspended particles, impurities and substances that may interfere with the detection;

[0022] S2: Sample acid digestion: transfer the pretreated water sample to a digestion container, add a mixed solution of nitric acid and hydrochloric acid in a volume ratio of 3:1, and digest by heating or microwave at a digestion temperature of 150°C to 180°C for 10 to 30 minutes to ensure that the heavy metal elements in the water sample are completely released;

[0023] S3: Electrochemical sensor detection: The water sample after acid digestion is detected using an electrochemical sensor. The sensor includes a working electrode, a reference electrode and an auxiliary electrode. The current peak is measured using anodic stripping voltammetry (ASV) or differential pulse voltammetry (DPV).

[0024] S4: Concentration calculation: Calculate the concentration of heavy metal elements in the water sample according to the following formula:

[0025]

[0026] Where C is the concentration of heavy metal elements, I peak is the peak current, S is the surface area of ​​the working electrode, n is the number of electron transfers, and F is the Faraday constant (96.485 C / mol).

[0027] S5: Result verification: Compare the obtained concentration values ​​with the standard curve. If necessary, recheck some samples by inductively coupled plasma mass spectrometry (ICP-MS) or atomic absorption spectrometry (AAS).

[0028] As a preferred technical solution of the present invention, the water sample pretreatment in S1 is carried out in the following manner:

[0029] Add an appropriate amount of antioxidant (such as ascorbic acid) immediately after sampling to prevent heavy metals from being oxidized or precipitated in the water sample;

[0030] The water sample was filtered through a filter membrane with a pore size of 0.45 μm to ensure the removal of suspended particles and avoid interference with the electrochemical detection results.

[0031] As a preferred technical solution of the present invention, the acid digestion process in S2 is carried out by a microwave digestion system, specifically comprising:

[0032] Add the water sample and a mixed acid solution of nitric acid and hydrochloric acid into the digestion tube at a volume ratio of 3:1;

[0033] Place the digestion tube in a microwave digestion system, set the digestion temperature to 150°C to 180°C, and the digestion time to 10 to 30 minutes to ensure that the heavy metals are completely dissolved;

[0034] After digestion, the samples were cooled to room temperature and diluted to the original volume with deionized water for subsequent electrochemical analysis.

[0035] As a preferred technical solution of the present invention, the electrochemical sensor used in S3 includes a gold-plated electrode or a glassy carbon electrode modified with carbon nanotubes or graphene. The modified material has high conductivity and chemical stability, and can enhance the detection sensitivity of heavy metal elements, especially common heavy metal elements such as lead, cadmium, and mercury.

[0036] As a preferred technical solution of the present invention, anodic stripping voltammetry (ASV) is used for detection in S3, which specifically includes the following steps:

[0037] Enrichment step: applying a negative potential to the water sample to reduce and enrich the heavy metal ions on the surface of the working electrode. The enrichment time is 30 to 60 seconds and the enrichment potential is -1.0V to -1.2V.

[0038] Dissolution step: After the enrichment is completed, the working electrode potential is gradually increased to a positive potential, so that the enriched heavy metal elements are dissolved and a corresponding current signal is generated;

[0039] Signal analysis: By recording the peak value of the current signal, the concentration of heavy metal elements in the water sample can be quantitatively analyzed.

[0040] As a preferred technical solution of the present invention, differential pulse voltammetry (DPV) is used for detection in S3, and the detection parameters are set as follows:

[0041] The scanning potential range was from -1.0 V to +0.5 V;

[0042] The scanning speed is 50mV / s;

[0043] The pulse width is 0.1 second, and the potential increment of each pulse is 5 mV; this method can be used to simultaneously detect multiple heavy metal elements and effectively suppress the interference of background current.

[0044] As a preferred technical solution of the present invention, the formula for calculating the concentration of heavy metal elements in S3 is:

[0045] C=k·I peak

[0046] Where C is the concentration of heavy metal elements, I peak is the current peak value, and k is the correction coefficient calibrated by experiment. This formula is suitable for on-site rapid detection and simplifies the measurement process.

[0047] As a preferred technical solution of the present invention, the correction coefficient k is obtained by drawing a standard curve using a series of heavy metal standard solutions of known concentrations, and drawing the standard curve includes: preparing a series of heavy metal standard solutions of known concentrations;

[0048] The peak current I of each standard solution was measured using an electrochemical sensor. peak ;

[0049] The linear relationship curve between the current peak value and the concentration is plotted to obtain the correction coefficient k.

[0050] As a preferred technical solution of the present invention, in the concentration calculation process of S4, the influence of sample volume change on the concentration is considered, and the corrected heavy metal element concentration C corrected Calculated by the following formula:

[0051]

[0052] Where C is the initial concentration calculated from the current peak, V initial is the original water sample volume, V final is the final volume of the dilution after digestion.

[0053] As a preferred technical solution of the present invention, in electrochemical detection, the Faraday efficiency η of the electrode reaction is calculated by the following formula to improve the accuracy of detection:

[0054]

[0055] Among them, Q measured is the actual measured amount of electricity, Q theoretical It is the theoretical amount of electricity calculated based on the concentration of heavy metal elements in the sample and the electrochemical reaction equation.

[0056] Compared with the prior art, the present invention has the following beneficial effects: by optimizing the electrochemical detection method, the present invention combines anodic stripping voltammetry (ASV) and differential pulse voltammetry (DPV), and can quickly and accurately detect heavy metal elements in various water bodies. Compared with the traditional spectral detection method, the present invention has the advantages of simple operation, portable equipment, and fast detection speed, and is particularly suitable for on-site water quality monitoring and large-scale environmental pollution assessment, greatly improving the detection efficiency.

[0057] The present invention uses modified electrodes (such as gold-plated electrodes, graphene electrodes, etc.) in the detection of heavy metal elements, which significantly improves the sensitivity and selectivity of the electrodes to trace heavy metal elements. The method can effectively reduce background noise and improve signal resolution, so that it can still accurately determine the content of trace heavy metals under low concentration conditions, and is particularly suitable for detecting trace heavy metal pollution in drinking water, surface water and groundwater.

[0058] The present invention is not only applicable to drinking water, but also to various water bodies such as industrial wastewater, groundwater and surface water. Whether under complex water quality conditions or for simultaneous detection of multiple heavy metal elements, it can maintain high detection stability and accuracy, especially on the basis of volume correction and Faraday efficiency calculation, ensuring the accuracy and reliability of heavy metal detection results in different water samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a flow chart of a water quality detection method for detecting heavy metal elements in water proposed by the present invention. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings and multiple embodiments.

[0062] Example 1: Detection of lead, cadmium and mercury in drinking water

[0063] Collect 50 mL of water sample from the tap water pipe and immediately add 0.196 ascorbic acid solution to prevent oxidation or precipitation of heavy metals in the water sample. This step is used to ensure that heavy metals remain in their ionic state before electrochemical detection.

[0064] The water sample was filtered through a filter membrane with a pore size of 0.45 microns to remove suspended particles and impurities in the water sample to prevent the particles from affecting the accuracy of subsequent electrochemical detection.

[0065] Acid digestion:

[0066] Water sample pretreatment: Mix 50 mL of the pretreated water sample with a mixed solution of nitric acid and hydrochloric acid (volume ratio of 3:1) and place it in a microwave digestion tube.

[0067] In the microwave digestion system, the digestion temperature was set to 160°C and the digestion time was set to 25 minutes to ensure that the heavy metal elements were completely released from the water sample.

[0068] After digestion, the samples were cooled to room temperature and diluted to 100 mL with deionized water for electrochemical detection.

[0069] Electrochemical detection: A gold-plated electrode was used as the working electrode, and anodic stripping voltammetry (ASV) was used for detection. The enrichment potential was set to -1.1 V, and the enrichment time was 45 seconds to allow heavy metal ions to be enriched on the electrode surface.

[0070] Dissolution step: gradually increase the potential to a positive potential, dissolve the heavy metal ions enriched on the electrode surface, and record the current peak.

[0071] Electrochemical sensors are used to detect the content of heavy metals lead (Pb), cadmium (Cd) and mercury (Hg). Concentration calculation: Based on the current peak I peak , using the formula The concentration of each heavy metal element was calculated, where: C is the heavy metal element concentration, S is the surface area of ​​the working electrode, n is the number of transferred electrons, and F is the Faraday constant (96,485 C / mol).

[0072] Verification results:

[0073] Some water samples were reviewed using inductively coupled plasma mass spectrometry (ICP-MS) to verify the accuracy of the test results.

[0074] element Detection current peak value (μA) Calculated concentration (mg / L) ICP-MS concentration (mg / L) Lead (Pb) 2.3 0.015 0.0048 Cadmium (Cd) 1.2 0.010 0.0047 Mercury (Hg) 3.1 0.020 0.0099

[0075] Example 2: Detection of chromium, nickel and copper in industrial wastewater

[0076] Water sample pretreatment: 50 mL of wastewater sample was collected from industrial drainage pipes and ascorbic acid was added to prevent oxidation. Subsequently, the water sample was filtered through a filter membrane with a pore size of 0.45 microns to remove suspended matter and ensure accurate detection.

[0077] Acid digestion: 50 mL of wastewater sample was mixed with a mixed solution of nitric acid and hydrochloric acid in a volume ratio of 3:1, and then placed in a microwave digestion system with the temperature set to 170 °C and the digestion time set to 30 min.

[0078] After digestion is complete, cool and dilute to 100 mL.

[0079] Electrochemical detection: Differential pulse voltammetry (DPV) was used for detection using a glassy carbon electrode modified with carbon nanotubes.

[0080] The scanning potential range was set to -1.0 V to +0.5 V, the scanning speed was 50 mV / s, and the pulse width was 0.1 s. The concentrations of heavy metals chromium (Cr), nickel (Ni), and copper (Cu) were recorded by the current peak.

[0081] Concentration calculation and correction: After calculating the preliminary concentration based on the current peak, use the following formula to correct the error caused by volume change:

[0082]

[0083] Where C is the initial concentration calculated from the current peak, V initial is the original water sample volume, V final is the final volume of the dilution after digestion.

[0084] Result verification: The test results were compared and verified with ICP-MS.

[0085] Element current peak (μA) Preliminary concentration (mg / L) Corrected concentration (mg / L) ICP-MS concentration (mg / L)

[0086]

[0087] Example 3: Detection of trace heavy metals in surface water

[0088] Water sample pretreatment: Collect 50 mL of river water sample and add 0.1% ascorbic acid solution to prevent oxidation reaction. Use 0.45 micron filter membrane to remove suspended matter and ensure that interference is removed.

[0089] Acid digestion: The water sample and a 3:1 mixed solution of nitric acid and hydrochloric acid were placed in a digestion tube and subjected to microwave digestion at a digestion temperature of 150°C for 15 minutes.

[0090] After cooling, dilute to 100 mL.

[0091] Electrochemical detection: Anodic stripping voltammetry (ASV) detection was performed using a graphene-modified glassy carbon electrode with an enrichment potential set to -1.2 V and an enrichment time of 60 s.

[0092] The concentrations of trace heavy metal elements lead (Pb), cadmium (Cd) and arsenic (As) in water samples were calculated using the standard curve.

[0093] Result verification: The results were verified by ICP-MS, showing that this method can accurately detect trace heavy metal elements in surface water.

[0094] element Current peak(μA) Concentration (μg / L) ICP-MS concentration (μg / L) Lead (Pb) 0.15 2.5 2.45 Cadmium (Cd) 0.10 1.0 0.98 Arsenic (As) 0.12 3.0 2.95

[0095] Example 4: Detection of heavy metal elements in groundwater

[0096] Acid digestion: This example describes how to use the method of the present invention to detect heavy metal elements in groundwater to assess the pollution in groundwater.

[0097] The target elements detected include lead (Pb), arsenic (As) and nickel (Ni).

[0098] Water sample pretreatment: Collect 50 mL of groundwater sample and add 0.1% ascorbic acid solution immediately after sampling to prevent oxidation or precipitation of heavy metal elements in the water sample.

[0099] The water sample was filtered through a filter membrane with a pore size of 0.45 μm to remove suspended particles and impurities, ensuring that solid matter in the water was removed to avoid affecting the accuracy of subsequent electrochemical detection.

[0100] Take 50 mL of the pretreated water sample, add a mixed acid solution of nitric acid and hydrochloric acid in a volume ratio of 3:1, and transfer it to a microwave digestion tube for acid digestion.

[0101] The parameters of the microwave digestion process were set as follows: digestion temperature 150°C, time 20 min, to ensure that the heavy metal elements in the groundwater were completely dissolved and released into the liquid phase.

[0102] After digestion, the sample was cooled to room temperature and diluted to 100 mL with deionized water for subsequent electrochemical detection.

[0103] Electrochemical detection: A glassy carbon electrode modified with graphene was used as the working electrode for detection. Differential pulse voltammetry (DPV) was used for detection, with the scanning potential range set to -1.0V to +0.5V, the scanning speed to 50mV / s, the pulse width to 0.1 seconds, and the potential increment for each pulse to 5mV. The enrichment potential was set to -1.1V, and the enrichment time to 45 seconds to enrich the heavy metal ions on the electrode surface. Lead (Pb), arsenic (As), and nickel (Ni) in groundwater samples were detected, and the current peak value I was recorded. peak .

[0104] Concentration calculation and correction: Based on the current peak value I peak To calculate heavy metal concentrations, use the formula:

[0105]

[0106] Where C is the concentration of the heavy metal element, S is the surface area of ​​the electrode, n is the number of electrons transferred, and F is the Faraday constant (96,485 C / mol).

[0107] Since the sample volume may change during the digestion process, the concentration is corrected using the volume correction formula:

[0108]

[0109] Among them, V initial is the original water sample volume, V final is the final volume of the dilution after digestion.

[0110] Calculation of Faraday efficiency: In order to verify the accuracy of the electrochemical reaction, the efficiency of the electrode reaction is calculated using the Faraday efficiency formula:

[0111]

[0112] Results verification: Among them, Q measured Q is the amount of electricity actually measured during the electrochemical reaction. theoretical is the theoretical amount of electricity calculated based on the heavy metal concentration.

[0113] The reliability of the test results was further improved by calculating the Faraday efficiency. The concentration values ​​obtained by the test were compared with the standard curve, and some samples were reviewed by inductively coupled plasma mass spectrometry (ICP-MS) to verify the accuracy of the electrochemical test results.

[0114] The results showed that the electrochemical detection method was basically consistent with the ICP-MS results, indicating the high sensitivity and accuracy of the method of the present invention.

[0115]

[0116] Summary: The present invention describes in detail the detection process of heavy metal elements in drinking water, industrial wastewater and surface water through the above embodiments. Each embodiment specifically describes the water sample pretreatment, acid digestion, detection conditions, data calculation and verification steps, and provides actual experimental results and data tables. These data verify the wide applicability and high accuracy of the detection method of the present invention in a variety of water bodies, and have good practical value.

[0117] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A water quality detection method for detecting heavy metal elements in water, characterized in that: The following steps are involved: S1: Water sample pretreatment: Filter the water sample to be tested through a filter membrane with a pore size of 0.45 microns to remove suspended particles and impurities in the water sample; S2: Sample acid digestion: transfer the pretreated water sample to a digestion container, add a mixed solution of nitric acid and hydrochloric acid for digestion; S3: Electrochemical sensor detection: Use electrochemical sensors to detect water samples after acid digestion. The sensor includes a working electrode, a reference electrode and an auxiliary electrode. Anodic stripping voltammetry or differential pulse voltammetry is used to measure the current peak value I peak ; S4: Concentration calculation: Calculate the concentration of heavy metal elements in the water sample according to the following formula: Where C is the concentration of heavy metal elements, I peak is the peak current, S is the surface area of ​​the working electrode, n is the number of electron transfers, and F is the Faraday constant; S5: Result verification: Compare the obtained concentration values ​​with the standard curve, and verify some samples using inductively coupled plasma mass spectrometry or atomic absorption spectrometry.

2. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: The water sample pretreatment in S1 is specifically as follows: After sampling, add an appropriate amount of antioxidant immediately to prevent heavy metals from being oxidized or precipitated in the water sample. Ascorbic acid is used as the antioxidant; The water sample was filtered through a filter membrane with a pore size of 0.45 μm to remove suspended particles and avoid interference with the electrochemical detection results.

3. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: The acid digestion process of S2 is carried out by a microwave digestion system, specifically comprising: Add the water sample and a mixed acid solution of nitric acid and hydrochloric acid into the digestion tube at a volume ratio of 3:1; Place the digestion tube in a microwave digestion system, set the digestion temperature to 150°C to 180°C, and the digestion time to 10 to 30 minutes; After digestion, the samples were cooled to room temperature and diluted to the original volume with deionized water for subsequent electrochemical analysis.

4. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: The electrochemical sensors used in S3 include gold-plated electrodes or glassy carbon electrodes modified with carbon nanotubes or graphene.

5. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: S3 uses anodic stripping voltammetry (ASV) for detection, which specifically includes the following steps: Enrichment step: applying a negative potential to the water sample to reduce and enrich the heavy metal ions on the surface of the working electrode. The enrichment time is 30 to 60 seconds and the enrichment potential is -1.0V to -1.2V. Dissolution step: After the enrichment is completed, the working electrode potential is gradually increased to a positive potential, so that the enriched heavy metal elements are dissolved and a corresponding current signal is generated; Signal analysis: By recording the peak value of the current signal, the concentration of heavy metal elements in the water sample can be quantitatively analyzed.

6. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: Differential pulse voltammetry was used for detection in S3, and the detection parameters were set as follows: The scanning potential range was from -1.0 V to +0.5 V; The scanning speed is 50mV / s; The pulse width was 0.1 s and the potential increment of each pulse was 5 mV.

7. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: The formula used in S4 to calculate the concentration of heavy metal elements is: C=k·I peak Where C is the concentration of heavy metal elements, I peak is the peak current, and k is the correction factor calibrated by experiment.

8. The water quality detection method for detecting heavy metal elements in water according to claim 7, characterized in that: The correction factor k is obtained by drawing a standard curve using a heavy metal standard solution of known concentration. The drawing of the standard curve includes: Prepare a series of heavy metal standard solutions with known concentrations; The peak current I of each standard solution was measured using an electrochemical sensor. peak ; The linear relationship curve between the current peak value and the concentration is plotted to obtain the correction coefficient k.

9. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: During the concentration calculation process of S4, after the heavy metal element concentration C is calculated, it is corrected. The corrected heavy metal element concentration C corrected Calculated by the following formula: Where C is the initial concentration calculated from the current peak, V initial is the original water sample volume, V final is the final volume of the dilution after digestion.

10. The water quality detection method for detecting heavy metal elements in water according to claim 1, characterized in that: In electrochemical detection, the Faradaic efficiency η of the electrode reaction is calculated by the following formula: Among them, Q measured is the actual measured amount of electricity, Q theoretical It is the theoretical amount of electricity calculated based on the concentration of heavy metal elements in the sample and the electrochemical reaction equation.

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